Polymorphic digital circuits are circuits composed of polymorphic (multifunctional) as well as ordinary gates. In addition to its standard logic function, a polymorphic gate exhibits another logic function which is activated under a specific condition, for example, when Vdd, temperature, illumination or a special signal reaches a certain level. In the recent years, several polymorphic gates have been discovered. These gates are designed using evolutionary approach and have some disadvantages what makes their application difficult. The paper refers about the effort to develop a set of polymorphic gates which eliminates main disadvantages of existing gates.